The present invention relates to an indexing device utilizing rotation of a main spindle of a machine tool such as a machining center.
An indexing device of the above character is disclosed in Japanese Utility Model Laid-Open Pub. No. Hei 1-84,943. In this indexing device, a clutch member is provided on the tip of an input shaft rotatably supported in the main body of the indexing device disposed on a work table of a machine tool. The clutch member is adapted to be engaged with a clutch member of a drive adapter detachably mounted on a main spindle of the machine tool to ensure that the rotation of the main spindle causes rotation of the input shaft. The indexing table is rotationally indexed by means of a Geneva mechanism incorporated in the main body. The indexing rotation of the Geneva mechanism is detected by an indexing detection switch disposed on the side of the main body, and the obtained indexing signals are transmitted to the side of the machine tool to stop the rotation of the main spindle of the machine tool.
As is disclosed in Japanese Patent Pub. No. Hei 12,003, 20,030, known is a tooth-shaped coupling interposed between a member to be indexed and a housing carrying the member to be indexed, the coupling serving as a means for preventing positional offset of the indexed position of the member to be indexed.
Furthermore, Japanese Patent Pub. No. Sho 63-39,752 discloses a positioning device in which the main spindle of the machine tool vertically moves a push bar, which in turn causes a swing lever to swing, to bring a positioning pin provided on the swing lever into and out of engagement with an engagement claw of an indexing table.
In the prior art described above, a signal line for transmitting signals, obtained by an indexing detection switch on the side of the indexing device, to the machine tool, independent from the indexing device, must be provided between the two. In this case, the indexing device is mounted on a pallet. Therefore, the signal line must be connected or disconnected when the pallet is automatically replaced, which makes it difficult to mount the indexing device onto the pallet.
Furthermore, in the device for preventing positional offset described above, in case a worm shaft has not rotated by an intended amount, a worm cannot be rotated due to self-lock of a worm wheel to eliminate the positional offset, in spite of an attempt for correction to a desired indexing position by engaging the tooth-shaped coupling.
In the positioning device described above, the positioning pin is engaged with and disengaged from the engagement claw by swinging movement of the swing lever, which necessitates a rather large space for the swinging movement, thus inconveniently leading to an increase in size of the entire device.